PROJECT SUMMARY/ABSTRACT Although the solution to occupational noise-induced hearing loss seems easy?train and provide hearing protectors to employees in high noise environments?hearing loss continues to be one of the most common work-related illnesses. According to the National Institute for Occupational Safety and Health, about 17% of all workers are exposed to hazardous noise (about 22 million workers). Yet, despite the implementation of industrial hearing conservation programs following OSHA's 1983 Hearing Conservation Amendment, the prevalence of noise-induced hearing loss decreased less than 1% over the last 30 years (1981?2010). Like most other personal protective equipment, hearing protection, especially earplugs, must be used properly to do their job. Proper use of earplugs requires two steps: (1) training proper insertion of earplugs and (2) testing after self-insertion of the earplug to ensure the training was effective (and to reinforce training over time). Research has shown that providing actual feedback on how well individuals don their hearing protectors has a significant impact on their ability to reliably achieve adequate protection. This technique is referred to as ?fit-testing.? Although systems have been developed to perform fit-testing, they require a trained administrator to perform the measurement. Creare, in collaboration with its clinical and research partners, proposes to develop a mobile low-cost fit-testing device, with integrated audiometer, to help noise-exposed workers confirm they are adequately protected and lower their daily exposure. Such an approach has the potential for high impact at very low cost because it requires minimal effort on the part of the employers and workers to greatly improve the existing hearing conservation programs.